JP5377134B2 - Method for producing colloidal silica - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a colloidal silica useful for an ink absorbing filler for printing papers, a spreading property improving agent for paint, a hydrophilic coating material for various material surfaces, a high strength binder, a high purity silica gel, a raw material for high purity ceramics, a binder for a catalyst, a polishing material for an electronic material and the like. <P>SOLUTION: The colloidal silica is produced by using an active silicic acid as a raw material in the presence of triazole, and contains triazole in the liquid phase and a group of non-spherical heteromorphic silica particles which has a major axis/minor axis ratio by a transmission electron microscope in the range of 1.0-5 and an average value of the major axis/minor axis ratio of 1.2-3. This can be produced by contacting an aqueous alkali silicate solution with a cation exchange resin to prepare an aqueous active silicic acid solution, thereafter adding triazole and an alkali agent to the aqueous active silicic acid solution to be made alkaline, and then heating to form silica particles and subsequently growing up the silica particles by a buildup technique. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an ink-absorbing filler for printing paper, a spreadability improving agent for paints, a hydrophilic coating material for various material surfaces, a high-strength binder, a high-purity silica gel, a raw material for high-purity ceramics, a binder for catalysts, and an electronic material. The present invention relates to a colloidal silica useful for abrasives for manufacturing and a method for producing the same.

  Many colloidal silicas composed of non-spherical silica particles have been proposed. In Patent Document 1, elongated amorphous colloidal silica particles having a uniform thickness within a range of 5 to 40 millimicrons by electron microscope observation and extending only in one plane are dispersed in a liquid medium. A stable silica sol is described. Patent Document 2 describes a silica sol composed of elongated silica particles obtained by a manufacturing method in which a metal compound such as an aluminum salt is added before, during or after the addition of a silicic acid solution. Patent Document 3 describes colloidal silica composed of bowl-shaped silica particles having a major axis / minor axis ratio of 1.4 to 2.2 obtained by hydrolysis of alkoxysilane. In Patent Document 4, a hydrolyzed solution of alkoxysilane is used instead of an active silicic acid aqueous solution of the water glass method, a tetraalkylammonium hydroxide is used as an alkali, and a colloid containing non-spherical silica particles. It is described that silica is obtained.

Further, many methods for reducing the content of alkali metal have been proposed for colloidal silica produced using alkali metal silicate (mainly sodium silicate) as a raw material. For example, Patent Document 5 describes that colloidal silica with less sodium can be obtained by using an active silicic acid aqueous solution of a water glass method and tetraalkylammonium hydroxide.
Even if sodium is removed by cation exchange from ordinary colloidal silica produced using water-silica active silicic acid aqueous solution and sodium hydroxide, the sodium present in the silica particles is gradually eluted into the liquid phase. It is well known. Therefore, in Patent Document 6, sodium is removed from colloidal silica by cation exchange, then ammonia is added to make it alkaline, and it is treated in an autoclave at 98 to 150 ° C. to forcibly remove sodium present in the silica particles. It describes a method of elution in the liquid phase and removal by cation exchange.

  On the other hand, triazole is used as a copper solubilizer because it forms a water-soluble complex salt with copper. Conversely, benzotriazole forms a water-insoluble complex salt with metals such as copper and silver, and therefore has applications as a copper corrosion inhibitor and photographic material. In recent years, as semiconductor wiring has shifted from aluminum to copper, triazole has expanded its application, and there are many patent documents describing triazole, although not as much as benzotriazole. When patent documents are illustrated, patent documents 7 to 9 describe that a copper film of a semiconductor is polished with a slurry containing triazole.

JP-A-1-317115 (Claims) Japanese Patent Laid-Open No. 4-187512 Japanese Patent Laid-Open No. 11-60232 (Claims) JP 2001-48520 A (Claims and Examples) JP 2003-89786 A JP 2004-189534 A (Claims) JP 11-238709 A JP 2004-259867 A JP 2005-129822 A

Since the colloidal silica described in Patent Document 1 includes a step of adding a water-soluble calcium salt, magnesium salt or a mixture thereof in the production process, they remain as impurities in the product. Since the colloidal silica described in Patent Document 2 includes a step of adding a water-soluble aluminum salt in the production process, they remain in the product as impurities.
Since the colloidal silica described in Patent Document 3 and Patent Document 4 uses alkoxysilane as a silica source, the product has high purity, but a recovery process for a large amount of by-product alcohol having a mole number four times that of silica is required. Another problem is that the price of alkoxysilane itself is high.
The colloidal silica described in Patent Document 5 is preferable in terms of a small amount of sodium, but no investigation has been made on the shape of the silica particles. The method for producing colloidal silica described in Patent Document 6 contains ammonia as an essential component, so that ammonia is contained inside the particles, which limits the application, and the production process is not long, resulting in an excessive use of energy, which is disadvantageous. There is one side.
In Patent Documents 7 to 9, no consideration is given to the shape of the abrasive particles.

  Accordingly, an object of the present invention is to produce a colloidal silica containing a non-spherical deformed silica particle group without using a polyvalent metal compound other than silicon such as calcium salt, magnesium salt, aluminum salt, and the production method thereof. It is providing the colloidal silica obtained by this.

As a result of intensive studies, the present inventors have been able to solve the above problems.
That is, the present invention includes the following steps:
(A) a step of bringing an alkali silicate aqueous solution into contact with a cation exchange resin to prepare an active silicate aqueous solution;
(B) adding triazole and an alkaline agent to the activated silicic acid aqueous solution to make it alkaline, and then heating to form silica particles; and
(C) Subsequently, while maintaining the alkalinity under heating, a step of adding an active silicic acid aqueous solution and triazole and an alkali agent, or adding an active silicic acid aqueous solution and an alkali agent to grow silica particles.
The liquid phase contains triazole, the major axis / minor axis ratio is 1.0 to 5 in the transmission electron microscope observation, and the average major axis / minor axis ratio is 1.2 to 3. This is a method for producing colloidal silica containing a group of spherical deformed silica particles .

Also, the manufacturing method of the colloidal silica after step (c) preferably further comprises a step of concentrating (d) is silica.
The formation of silica particles and the growth of silica particles may be collectively referred to as “particle growth” or “growth” below.

  The manufacturing method of the said colloidal silica is substantially the same as the manufacturing method which used the alkali metal hydroxide and alkali silicate which are the usual methods for the alkali agent. That is, in the method for producing colloidal silica, the process for producing an active silicic acid aqueous solution from sodium silicate is the same as that in a conventional method, except that triazole and an alkali agent are used in the growth process of forming silica particles. In the step of growing silica particles, triazole may or may not be added. The step of concentrating the obtained colloidal silica is the same as the conventional method. The alkali agent may be an alkali metal hydroxide used in a conventional manner or an organic alkali.

  According to the present invention, an ink-absorbing filler for printing paper, a spreadability improving agent for paints, a hydrophilic coating material on the surface of various materials, a high-strength binder, a high-purity silica gel, a raw material for high-purity ceramics, a binder for catalysts, Colloidal silica useful as an abrasive for electronic materials can be provided at low cost.

2 is a TEM photograph of colloidal silica that has undergone the silica particle forming step of Example 1. FIG. 2 is a TEM photograph of colloidal silica obtained in Example 1. FIG.

The present invention will be further described below.
The colloidal silica of the present invention is obtained using an active silicic acid aqueous solution as a raw material in the presence of triazole. The colloidal silica of the present invention is a non-spherical deformed silica having a major axis / minor axis ratio in the range of 1.0 to 5 and an average value of the major axis / minor axis ratio of 1.2 to 3 by observation with a transmission electron microscope. Contains particles. The major axis / minor axis ratio in the present invention is determined by assigning a scale to the obtained transmission electron micrograph of colloidal silica and, for 100 randomly selected silica particles, the longest side a and the shortest side b of the silica particles. , And using this value (a1, a2,..., A100 and b1, b2,..., B100), the major axis / minor axis ratio (a1 / b1, a2 / b2,... A100 / b100) is calculated, and the arithmetic average value of the five values on the minimum value side is set as the upper limit, and the arithmetic average value of the five values on the maximum value side is set as the lower limit. The average value of the major axis / minor axis ratio in the present invention refers to the longest side a of the silica particles of 100 randomly selected silica particles by assigning a scale to the obtained transmission electron micrograph of colloidal silica. And the shortest side b, and using this value (a1, a2,..., A100 and b1, b2,..., B100), the major axis / minor axis ratio (a1 / b1, a2 / b2,..., a100 / b100), and is an arithmetic average value of 90 values excluding 5 values on the maximum value side and the minimum value side.

  The colloidal silica of the present invention contains triazole in the liquid phase. This triazole is used during the formation and growth of colloidal particles. In the colloidal silica of the present invention, the preferred silica / triazole molar ratio is in the range of 15 to 2,000. The logarithmic values (pKa) of the reciprocal of acid dissociation constants of 1,2,3-triazole and 1,2,4-triazole are 1.2 and 2.3, respectively, which are weak bases. For example, a 1% aqueous solution of 1,2,4-triazole has a pH of about 6 and does not contribute to particle growth. However, it affects the particle shape during particle formation and particle growth. Triazole seems to be bound or adsorbed on the surface of growing silica particles to inhibit particle growth at the binding site and prevent spherical growth. The silica / triazole molar ratio when the silica gel was generated was less than 15. This is probably because the concentration of triazole was too high and particle growth was not possible at all. The silica / triazole molar ratio was greater than 2,000 when it contained many silica particles that were nearly spherical in shape. This is probably because the triazole concentration is low and the effect of inhibiting the particle growth is small. Therefore, in the colloidal silica in which the non-spherical silica particles are predominant, the silica / triazole molar ratio is in the above range. However, when concentrating by ultrafiltration, this triazole decreases with water, so the final product may have a silica / triazole molar ratio of over 2,000. In addition, triazole may be added to the colloidal silica after the concentration step to make the silica / triazole molar ratio in the final product less than 15.

  The colloidal silica containing the non-spherical irregular-shaped silica particle group in the present invention is a colloidal shape having a cocoon-like shape or a bent rod-like shape such as a worm, and containing silica particles having different shapes. Silica. Specifically, it is colloidal silica containing silica particles having a shape as shown in FIGS. The major axis / minor axis ratio of the silica particles is in the range of 1.0 to 5. Most of the silica particles are non-spherical particles, and some particles are nearly spherical. The silica particles shown in FIG. 1 and FIG. 2 are examples, and the shapes thereof vary depending on the production conditions. However, in the colloidal silica of the present invention, the non-spherical silica particles occupy the majority.

  The silica particles contained in the colloidal silica of the present invention have a shape very similar to that of fumed silica. The silica particles of fumed silica are generally a group of elongated deformed silica particles having a major axis / minor axis ratio of 5 to 15. The primary particle diameter of fumed silica (sometimes simply referred to as the particle diameter) is the short diameter (thickness) of the primary particles and is usually 7 to 40 nm. Further, the primary particles aggregate to form secondary particles, and the appearance of the slurry is white. For this reason, there are defects such as a problem that the particles settle when the slurry is left for a long time and a transparent film or coating film is not formed.

  However, the silica particles contained in the colloidal silica of the present invention do not form secondary particles due to aggregation as seen in fumed silica, and the appearance of the slurry is transparent or translucent. There is no problem that the particles settle, and a transparent film or coating film can be obtained.

  The method for producing colloidal silica of the present invention is characterized in that an active silicic acid aqueous solution of a water glass method is used as a silica source, and triazole and an alkali agent are used in the particle forming step. In the particle forming process, the presence of triazole is indispensable. On the other hand, in the particle growth step, since the triazole added in the previous step remains in the liquid phase, the silica particles may be grown by adding only the active silicic acid aqueous solution and the alkali agent, but the active silicic acid aqueous solution, triazole and Silica particles may be grown by adding an alkali agent.

  As the alkali agent, an alkali metal hydroxide such as sodium hydroxide is the most suitable material. When alkali metals are not preferred, nitrogen-containing organic alkali compounds such as amines and quaternary ammonium hydroxide can be used. As amines, tertiary amines with low volatility such as triethanolamine, secondary amines such as piperazine, and aliphatic amines such as ethylenediamine can be used. Examples of the quaternary ammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and trimethyl-2-hydroxyethylammonium hydroxide (also known as choline hydroxide).

  By using the nitrogen-containing organic alkali compound, the alkali metal content per silica can be 50 ppm or less. In applications such as ceramics, binders for catalysts, abrasives for electronic materials, etc., it is necessary to have such an alkali metal content. More preferably, it is 30 ppm or less.

  As the alkali silicate aqueous solution used as a raw material, usually a sodium silicate aqueous solution called water glass (water glass No. 1 to No. 4 etc.) is preferably used. This is relatively inexpensive and can be easily obtained. Moreover, in the semiconductor use which dislikes Na ion, it is preferable to use a potassium silicate aqueous solution as a raw material instead of a sodium silicate aqueous solution. There is also a method of preparing an alkali silicate aqueous solution by dissolving a solid alkali metal silicate in water. Alkali metasilicates are produced through a crystallization process, and therefore some of them have few impurities. The aqueous alkali silicate solution is diluted with water as necessary.

  The cation exchange resin used in the present invention can be appropriately selected from known ones and is not particularly limited. The contact step between the aqueous alkali silicate solution and the cation exchange resin is, for example, diluted with an aqueous alkali silicate aqueous solution to a silica concentration of 3 to 10% by weight, then contacted with an H-type strongly acidic cation exchange resin for dealkalization, and if necessary It can carry out by making it contact with OH type strong basic anion exchange resin, and carrying out a deanion. By this step, an active silicic acid aqueous solution is prepared. There have been various proposals for details of the contact conditions, and any known conditions can be adopted in the present invention.

  Next, silica particles are formed. In this particle forming step, a conventional operation is performed except that triazole is added to the active silicic acid aqueous solution. For example, silica particles (seed particles) can be formed by adding triazole and an alkali agent to an active silicic acid aqueous solution so as to have a pH of 8 or more and heating to 60 to 240 ° C. Either the triazole or the alkali agent may be added first.

  Next, particle growth is performed using a build-up method using the silica particles formed above as a seed sol. In this particle growth step, a seed sol having a pH of 8 or higher is heated to 60 to 240 ° C., and while maintaining the pH at 8 to 11, an active silicic acid aqueous solution, a triazole and an alkali agent are added, or an active silicic acid aqueous solution. And an alkali agent are added to grow silica particles. In this way, the average minor axis of the silica particles is preferably 5 to 30 nm.

  The colloidal silica obtained through the particle formation step and the particle growth step may be concentrated as necessary. The silica may be concentrated by evaporating water, but in terms of energy, ultrafiltration is more advantageous.

  The ultrafiltration membrane used when concentrating silica by ultrafiltration will be described. Separation to which the ultrafiltration membrane is applied targets particles of 1 nm to several microns, but also targets dissolved polymer substances, and therefore, filtration accuracy is expressed by a molecular weight cut off in the nanometer range. In the present invention, an ultrafiltration membrane having a fractional molecular weight of 15,000 or less can be preferably used. When a film in this range is used, particles of 1 nm or more can be separated. More preferably, an ultrafiltration membrane having a fractional molecular weight of 3,000 to 15,000 is used. If the membrane is less than 3,000, the filtration resistance is too large and the treatment time becomes long and uneconomical. If it exceeds 15,000, the degree of purification is low. The material of the membrane includes polysulfone, polyacrylonitrile, sintered metal, ceramic, carbon, etc., any of which can be used. Polysulfone membranes are easy to use in terms of heat resistance and filtration speed. The shape of the membrane includes a spiral type, a tubular type, and a hollow fiber type, and any of them can be used. Hollow fiber membrane is compact and easy to use. In addition, if the ultrafiltration process also serves to wash out and remove excess triazole, it is further washed out and removed by adding pure water after reaching the target silica concentration, if necessary, to remove triazole. You can also work to increase the rate. It is good to concentrate so that the density | concentration of a silica may be 5 to 50 weight% at this process.

  Moreover, in this invention, you may refine | purify the obtained colloidal silica with an ion exchange resin after a particle growth process or an ultrafiltration process as needed. For example, the colloidal silica is contacted with an H-type strongly acidic cation exchange resin to remove the alkaline agent, or the colloidal silica is contacted with an OH-type strongly basic anion exchange resin to deanion to further increase the purity. Can be planned.

  As described above, by producing colloidal silica using an active silicic acid aqueous solution as a raw material in the presence of triazole, the liquid phase contains triazole, and the major axis / minor axis ratio by observation with a transmission electron microscope is 1.0-5. And colloidal silica containing non-spherical irregularly shaped silica particles having an average value of the major axis / minor axis ratio of 1.2 to 3 can be obtained. The colloidal silica thus obtained contains no polyvalent metal compounds other than silicon such as calcium salt, magnesium salt, aluminum salt, etc., so that the ink absorbent filler for printing paper, the paint spreadability improving agent, It is useful for hydrophilic coating materials on the surfaces of various materials, high-strength binders, high-purity silica gel, raw materials for high-purity ceramics, binders for catalysts, abrasives for electronic materials, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples. The following apparatus was used for the measurement in the examples.
(1) TEM observation: Hitachi, Ltd., transmission electron microscope H-7500 type was used.
(2) BET specific surface area: Shimadzu Corporation, Flowsorb 2300 type was used.
(3) Triazole analysis: Shimadzu Corporation, total organic carbon meter TOC-5000A and solid sample combustion apparatus SSM-5000A were used, and converted into triazole from the total organic carbon amount obtained. Specifically, the total organic carbon amount (TOC) was determined by TOC = TC-IC after measuring the total carbon amount (TC) and the inorganic carbon amount (IC). The IC component is estimated to be carbon dioxide absorbed from the atmosphere.
For the measurement of triazole in colloidal silica, Shimadzu Corporation, Total Organic Carbon Meter TOC-5000A and Solid Sample Combustor SSM-5000A were used. A glucose aqueous solution having a carbon content of 0.02 wt% was used as a standard for TC measurement, and a sodium carbonate aqueous solution having a carbon content of 0.02 wt% was used as a standard for IC measurement. A calibration curve was prepared using ultrapure water as a standard with a carbon content of 0% by weight, using the above-mentioned standards, TC of 125 μl and 250 μl, and IC of 100 μl. In the TC measurement of the sample, about 100 mg of the sample was collected and burned in a 900 ° C. combustion furnace. In IC measurement, about 100 mg of a sample was collected, about 0.5 ml of (1 + 1) phosphoric acid was added, and the reaction was promoted in a 200 ° C. combustion furnace.
Moreover, Shimadzu Corporation Corporation and the total organic carbon meter TOC-5000A were used for the measurement of the triazole of the filtrate at the time of ultrafiltration. As TC measurement standards, calibration curves were prepared using 32 μl each of an aqueous solution of potassium hydrogen phthalate having a carbon content of 0.05% by weight and a carbon content of 0.02% and an ultrapure water having a carbon content of 0% by weight. Calibration curves were prepared using 40 μl each of a mixed aqueous solution of sodium hydrogen carbonate and sodium carbonate having a carbon content of 0.05% by weight and carbon content of 0.02% and ultrapure water having a carbon content of 0% by weight as IC measurement standards. did. In the TC measurement of the sample, 32 μl of the sample was used and burned in a 680 ° C. combustion tube. In IC measurement, 40 μl of the sample was used and reacted with (1 + 1) phosphoric acid.
Further, in the sample containing tetramethylammonium hydroxide, tetramethylammonium was quantified by the following method (5), subtracted from TC, and converted to the triazole amount.
(4) Metal element analysis: HORIBA, Ltd., ICP emission spectrometer, ULTIMA2 was used.
(5) Ion chromatographic analysis of tetramethylammonium (TMA): Dionex Corporation, ion chromatography ICS-1500 was used. Specifically, the liquid phase TMA was measured by diluting a sample with pure water from 1,000 times to 5,000 times. For the measurement of total TMA, 3 g of 20 wt% NaOH and pure water was added to 5 g of sample as a pretreatment, and heated at 80 ° C. to completely dissolve silica. This solution was diluted with pure water from 1,000 times to 5,000 times and measured to obtain the amount of TMA.

[Example 1]
(A) Preparation of active silicic acid aqueous solution deionized water 28kg No. 3 sodium silicate (SiO _2: 28.8 wt%, Na ₂ O: 9.7 wt%, H ₂ O: 61.5 wt%) 5.2 kg Was added and mixed uniformly to prepare diluted sodium silicate having a silica concentration of 4.5% by weight. This diluted sodium silicate was passed through a 20 liter column of H-type strongly acidic cation exchange resin (Amberlite (registered trademark) IR120B manufactured by Organo Corp.) regenerated with hydrochloric acid in advance, and the silica concentration was 3.7% by weight. 40 kg of an active silicic acid aqueous solution having a pH of 2.9 was obtained.

(B) Formation of Silica Particles Next, triazole was added to the obtained active silicic acid aqueous solution, and then an alkali agent was added to make the solution alkaline and heated to form silica particles. That is, 1 g of 1,2,4-triazole (reagent, powder) was added to 500 g of a part of the obtained active silicic acid aqueous solution with stirring, and then 5 wt% aqueous sodium hydroxide solution was added to adjust the pH. 8.2, kept at 100 ° C. for 1 hour, and allowed to cool.

The obtained colloidal silica was 460 g by evaporation of water, and the silica concentration was 4.0% by weight. Further, the obtained colloidal silica has a pH of 9.6 at 25 ° C., and has a minor axis of about 5 nm and a major axis / minor axis ratio in the range of 1 to 5 as observed with a transmission electron microscope (TEM). And it consisted of the non-spherical irregular-shaped silica particle group whose average value of major axis / minor axis ratio is 2. A TEM photograph is shown in FIG.
The colloidal silica was calculated to have a silica / triazole molar ratio of 21 from the amount of active silicic acid aqueous solution used, the amount of triazole used and the analytical value. The total triazole concentration of the colloidal silica was 0.217% by weight.

(C) Growth of Silica Particles Subsequently, the obtained colloidal silica was heated again to 100 ° C., a build-up method was taken, and 3,000 g of an active silicic acid aqueous solution was added over 5 hours. During the addition of the active silicic acid aqueous solution, a 5% by weight sodium hydroxide aqueous solution was simultaneously added so that the pH was in the range of 9 to 10 while maintaining 100 ° C. After cooling by evaporation of water during the addition, 2,760 g of colloidal silica was obtained. The silica concentration was 4.7% by weight. The colloidal silica has a pH of 9.5 at 25 ° C., a short diameter of about 10 to 20 nm, a long diameter / short diameter ratio in the range of 1 to 3, and a long diameter as observed with a transmission electron microscope (TEM). / It consisted of a group of non-spherical deformed silica particles having an average value of the minor axis ratio of 2. A TEM photograph is shown in FIG. The particle diameter in terms of specific surface area by BET method was 17 nm.
The colloidal silica was calculated to have a silica / triazole molar ratio of 150 from the amount of active silicic acid aqueous solution used, the amount of triazole used and the analytical value. The total triazole concentration of the colloidal silica was 0.036% by weight.

(D) Concentration of colloidal silica Finally, by pump circulation using a hollow fiber type ultrafiltration membrane having a molecular weight cut off of 6,000 (Microsa (registered trademark) UF module SIP-1013 manufactured by Asahi Kasei Co., Ltd.) Pressure filtration was performed to concentrate the colloidal silica to a silica concentration of 26.9% by weight, and about 480 g of colloidal silica was recovered. The colloidal silica has a pH of 8.9 at 25 ° C., a short diameter of about 10 to 20 nm, a long diameter / short diameter ratio in the range of 1 to 3 and a long diameter as observed with a transmission electron microscope (TEM). / It consisted of a group of non-spherical deformed silica particles having an average value of the minor axis ratio of 2.
This colloidal silica was calculated to have a silica / triazole molar ratio of 1,000 based on the amount of active silicic acid aqueous solution used and the analysis value of triazole. The total triazole concentration of the colloidal silica was 0.031% by weight.
Since the triazole concentration of the filtrate at the time of ultrafiltration was 0.043% by weight, it was confirmed that triazole could be efficiently removed by ultrafiltration. The content of alkali metal per silica was 16,700 ppm.

[Example 2]
To 500 g of the same active silicic acid aqueous solution used in Example 1, 0.5 g of 1,2,3-triazole (reagent, liquid) was added and dissolved with stirring, and then a 25 wt% tetramethylammonium hydroxide aqueous solution was added. After 12 g was added to adjust the pH to 8.2, the mixture was kept at 100 ° C. for 1 hour and allowed to cool.
The obtained colloidal silica has a pH of 9.7 at 25 ° C., a short diameter of about 5 nm, a long diameter / short diameter ratio in the range of 2 to 15 and a long diameter as observed with a transmission electron microscope (TEM). / It consisted of non-spherical irregularly shaped silica particles having an average minor axis ratio of 10.

  Subsequently, the obtained colloidal silica was heated again to 100 ° C., and 2,000 g of an active silicic acid aqueous solution was added over 4 hours. During the addition of the active silicic acid aqueous solution, 6 g of a 25 wt% tetramethylammonium hydroxide aqueous solution was simultaneously added so that the pH was in the range of 9 to 10 while maintaining 100 ° C. After cooling by evaporation of water during addition, 2,100 g of colloidal silica was obtained. The silica concentration was 4.4% by weight. This colloidal silica has a pH of 9.5 at 25 ° C., and has a minor axis of about 10 to 15 nm and a major axis / minor axis ratio in the range of 1.2 to 5 as observed with a transmission electron microscope (TEM). And it consisted of the non-spherical irregular-shaped silica particle group whose average value of major axis / minor axis ratio is 2. The particle diameter in terms of specific surface area by BET method was 9 nm.

Finally, pressure filtration by pump circulation is performed using a hollow fiber type ultrafiltration membrane with a molecular weight cut off of 6,000 (Microsa (registered trademark) UF module SIP-1013 manufactured by Asahi Kasei Co., Ltd.), and silica Colloidal silica was concentrated to a concentration of 18.5% by weight, and about 500 g of colloidal silica was recovered. This colloidal silica has a pH of 9.1 at 25 ° C., a transmission electron microscope (TEM) observation has a minor axis of about 10 to 15 nm and a major axis / minor axis ratio of 1.2 to 5. And it consisted of the non-spherical irregular-shaped silica particle group whose average value of major axis / minor axis ratio is 2.
The colloidal silica was calculated to have a silica / triazole molar ratio of 1,330 from the amount of active silicic acid aqueous solution used and the analysis value of triazole. The total triazole concentration of the colloidal silica was 0.025% by weight.
Since the triazole concentration of the filtrate at the time of ultrafiltration was 0.023% by weight, it was confirmed that triazole could be efficiently removed by ultrafiltration. The alkali metal content per silica was 30 ppm.

Claims (2)

The following steps: (a) A step of bringing an alkali silicate aqueous solution into contact with a cation exchange resin to prepare an active silicate aqueous solution;
(B) a step of adding triazole and an alkali agent to the activated silicic acid aqueous solution to make it alkaline, and then heating to form silica particles, and (c) subsequently, while maintaining alkalinity under heating, Addition of silicic acid aqueous solution and triazole and alkali agent, or addition of active silicic acid aqueous solution and alkali agent, and having a step of growing silica particles , containing triazole in liquid phase, transmission type Production of colloidal silica containing non-spherical deformed silica particles having a major axis / minor axis ratio in the range of 1.0 to 5 and an average value of major axis / minor axis ratio of 1.2 to 3 by electron microscope observation Method. The method for producing colloidal silica according to claim 1 , further comprising (d) a step of concentrating silica after the step (c).

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